HYBRIDISING AND SELECTION 27 



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on the other hand, has to bring about the fertilisation of the flower of one 

 species or variety by the pollen of another of his own choosing. His aim 

 is usually to unite in the progeny qualities in the parents severally 

 possessed, such as hardiness or better habit with greater flower beauty. 

 There are limits, of course, to the choice of parents, just as there are in 

 the animal world. Species of the same genus are capable as a rule of 

 being hybridised, although sometimes physical divergences prevent it. 

 Occasionally, too, species of different but closely allied genera will cross- 

 breed. Progeny of the more distantly related parents are generally 

 barren. 



To secure hybridisation two essential points must be borne in mind : 

 viz., the stigma should be in a receptive condition, and the impregnation 

 of the flower by pollen from any other flower than the one selected by the 

 operator must be prevented. 



The stigma usually indicates its readiness to receive the pollen by 

 becoming sticky, but it is often desirable to dust it over afresh with pollen 

 every day for a few days after the viscidity appears. 



The first thing to do in regard to the other point is to protect it from 

 its own pollen. With plants left to themselves, Nature usually secures 

 this herself, but not always. The hybridiser leaves as little as possible to 

 chance, and so the careful operator commences by removing the stamens 

 from the flower he wishes to cross-fertilise, and to do this effectually he 

 breaks open the flower before it expands naturally, and cuts away the 

 anthers before the pollen has become ripe (i.e. dust-like). If it be a 

 small shrub, it is often advisable to take it up and keep it in a cool airy 

 glass-house until the impregnating process is over. The only danger 

 then is that a stray bee or other insect may enter and deposit foreign 

 pollen on the stigma ; but if the petals be removed as well as the stamens 

 the danger is a very remote one. All flowers other than those impreg- 

 nated must be removed. 



Out-of-doors, owing to wind, insects, and other disturbing agencies, the 

 process is not so much under control. The removal of the stamens from 

 the flower to be impregnated is again necessary before the petals expand ; 

 and to prevent a fertilisation other than the desired one, it is usual to 

 enclose that part of the branchlet bearing the flower with white gauze or 

 transparent paper, unless the shrub or tree is in a well-isolated position. 

 The removal of the stamens is best accomplished by the aid of a pair 

 of finely pointed scissors, and it is scarcely needful to say that all bruising 

 and scratching of the pistil is to be avoided. The fertilised flower should 

 be ticketed with a number corresponding to one in a note-book, under 

 which particulars as to parentage, dates, etc., are entered. As soon as 

 the flowering season is past, and consequently all danger of chance impreg- 

 nation over, the gauze or paper guards must be removed. 



